1. Field of the Invention
The present invention relates to a storage subsystem and a storage-subsystem control method.
2. Description of the Related Art
A storage subsystem is capable of providing a host computer with large-capacity and high performance storage services. In a storage subsystem, a multiplicity of disk drives is arranged in the form of an array and storage regions based on RAID (Redundant Array of Independent Inexpensive Disks) are constructed, for example. Logical volumes constituting logical storage regions are formed in the physical storage region that each disk drive comprises. An LUN (Logical Unit Number) is associated beforehand with each logical volume. The host computer issues a write command or read command of a predetermined format to the storage subsystem by specifying an LUN or block address. As a result, the host computer is able to write and read desired data to and from the storage subsystem.
A plurality of host computers can be connected to the storage subsystem. Problems sometimes arise when a data group managed by a certain host computer or application program can be read or written by another host computer or application program. Therefore, access control technology such as zoning, LUN masking, and so forth, for example, may be used. Zoning is a technology that sets one or a plurality of zones in the storage subsystem and allows a data transfer to only a specified communication port or WWN (World Wide Name) that belongs to the zone. LUN masking is a technology that allows a specified host computer access to a specified LUN.
Therefore, the exchange of data between a host computer and a disk drive is executed via cache memory. When a write command is output by the host computer, data is temporarily stored in cache memory and then written to the disk drive, for example. Further, when a read command is output by the host computer, data that is read from the disk drive is supplied to the host computer via the cache memory, for example. Therefore, technology that suitably allocates a cache memory quota to a disk drive is also known (Japanese Patent Application Laid Open No. H4-264940)
Access restrictions that restrict access by a host computer to the storage subsystem can be established by means of conventional zoning, LUN masking, and so forth. However, with the conventional technology, only simple access restrictions for a logical volume are possible and partition management for the resources of the storage subsystem is not implemented, meaning that ease of use is poor. In cases where the storage subsystem is used jointly by a plurality of users, when a certain user issues a large quantity of input/output requests (IO requests), for example, multiple cache-memory regions are used to process these requests. Therefore, sufficient cache memory cannot be used for the input/output processing by other users and the service capacity of the subsystem as a whole is reduced. That is, in providing one user with services, services supplied to another user are affected.
Further, although, according to the technology of Japanese Patent Application No. H4-264940, cache memory is allocated to each storage device, data stored in cache memory is efficiently written to the storage devices but resource (cache memory) partition management is not performed in order to service a plurality of users.